Reconstituted tobacco leaf, that is, tobacco sheet, also known as reconstituted tobacco or homogenized tobacco, is produced mainly from tobacco dust, stems, low-grade tobacco leaves, and additional foreign fibers, adhesives or other additives. As a kind of material widely used in tobacco product, reconstituted tobacco has the advantages of low cost, good filling performance, less tar content in the smoke, and so on. The production of reconstituted tobacco began in the '50s of the 20th century. Its production processes mainly include slurry process, rolling process and paper-making process, and the paper-making process is further divided into wet paper-making process and air-laid paper-making process. However, being it wet paper-making process or air-laid paper-making process, plant fiber pulp boards have to be fiberized for further formation. The wet paper-making process uses a first-level refiner and a second-level refiner to moderately grind fibers to make them become individualized after using a hydrapulper to crush the pulp boards. These fibers will then become pulp after being beat and fibrillated in the water. The pulp will then be put in a pulp tank for use after it is processed by a high-density sand remover and a tickler. As for the air-laid paper-making process, it fiberizes the fibers in the air without water. Usually, it uses high-speed rotating needle dials, hammers, claw disks or second-level crushing devices to fiberize the fibers to make them individualized.
After 20 years of research and use, this technology is quite well developed and has been widely used tobacco products. However, it still has some problems. Firstly, after the processes of extracting, concentrating and refining, scent and aroma of the tobacco are significantly reduced. Secondly, the reconstituted tobacco produced by this process is structurally solid and slick on the surface. Therefore, it has lower weight gain (normally less than 40%) and lacks taste. Thirdly, it produces large amounts of wastewater. In order to overcome the disadvantages of traditional wet paper-making processes, and to reduce environmental pollution and harmful components in China, a new process and equipment in this field for improving the quality of reconstituted tobacco and reducing environment pollution has to be developed.
A new kind of equipment using air-laid paper-making process to produce reconstituted tobacco can not only protect the environment by reducing the large amount of sewage discharge generated during the production but also prevent aroma loss in reconstituted tobacco. Its weight gain on the base sheets can be increased to more than 200%, and both filling power and wet strength has improved. Compared with traditional paper-making process, it can also reduce more harmful aspects in the smoke.
The air-laid paper-making process was born in the '60s of the 20th century and introduced into China at the end of the '80s of the 20th century. After 20 years of development, the air-laid paper-making process has become fully mature and well-known. For example, Chinese Patent Application No. 200610117771.4 discloses a paper-making machine that uses aid-laid process. Moreover, a Chinese patent No. 201310393610.8 discloses a complete production line that uses air-laid process to produce reconstituted tobacco. Other than having two more adhesive and drying devices, the machine has no different from ordinary air-laid paper-making machine in terms of manufacturing techniques. It does not have special devices, especially fiberizing, forming, sizing and drying devices, necessary for producing reconstituted tobacco. Even the most well-known wet paper-making machine cannot be used directly to produce reconstituted tobacco, instead, corresponding devices required by the nature of reconstituted tobacco has to be designed for production of the same. Similarly, an ordinary air-laid paper-making machine cannot be used directly to produce reconstituted tobacco either; instead, corresponding devices required by the nature of reconstituted tobacco has to be designed or added for production of the same.